Merry, 
Thank you for your question. 

Peanut butter has a long shelf life. The 'best by' date refers to the quality of the peanut butter (meaning it is best when you use it by that date). 'Best By" is not a statement related to food safety. https://ask.usda.gov/s/article/Is-food-safe-after-the-date-expires 

According to the National Peanut Board commercially processed peanut butter can last up to 9 months in a pantry. If opened it lasts about 3 months in the pantry or 9 months if stored in the refrigerator.  

Please be aware that natural peanut butter has a shorter shelf life because it doesn't have preservatives. Whether opened or unopened it lasts about 6 months in the refrigerator. 

TIPS: 
When products have an 800 number on the label, you can get the companies recommendation for the specific product. 

If you decide not to go ahead and use the peanut butter, you can feed birds and squirrels by using a knife or spoon the add peanut butter on and into a pinecone with a string tied around it, so you can hang it in a tree.

If you have further questions, you may email: Pat Holmes, Ohio State University Extension, Montgomery County
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Thank you for thinking of Extension.